Background Postoperative pain in pediatrics causes psychological and physiological problems; thus, preemptive analgesia is important, even in newborns. Caudal block is a useful adjuvant with general anesthesia and for postoperative analgesia for infraumbilical operations. Levobupivacaine is less cardiotoxic, less neurotoxic, and an equally potent local anesthetic compared with its racemate.Aim Our aim is to compare the efficacy of caudally administered isobaric levobupivacaine 0.25% versus isobaric bupivacaine 0.25% in children undergoing lower abdominal surgery.Patients and methods This study was carried out on 60 children, 1–10 years, American Society of Anesthesiologists I–II, scheduled for elective lower abdominal surgery. Patients were randomized into two equal groups (30 patients in each group): group I: bupivacaine group: patients received 1 ml/kg bupivacaine 0.25%. Group II: levobupivacaine group: patients received 1 ml/kg levobupivacaine 0.25%. The onset time of sensory block, heart rate, mean arterial blood pressure, and respiratory rate were recorded intraoperatively. Postoperative pain was assessed using the Children’s and Infant’s Postoperative Pain Scale; time of postoperative first rescue of analgesia and duration of motor blockade were determined by the Bromage score postoperatively.Results There was no significant difference between both groups in the onset time of sensory block, hemodynamics (heart rate and mean arterial pressure), and respiratory rate. Children’s and Infant’s Postoperative Pain Scale was significantly lower in group I at 120 and 180 min postoperatively. The Bromage score was significantly lower in group ІІ at 15, 30, and 60 min postoperatively. Time till administration of first-rescue analgesia was significantly shorter in group II than group I.Conclusion Using similar doses, bupivacaine produced a higher incidence of residual motor block and longer analgesic block than levobupivacaine. Thus, levobupivacaine is more suitable for short operations and could make it preferable for day case surgery. However, bupivacaine is still more suitable for prolonged operations.

Postoperative pain management in pediatrics is important for medical and ethical reasons. Postoperative pain management increases patient satisfaction and decreases the period of hospital stay [1]. Adequate postoperative analgesia in pediatrics is essential; however, the side effects of various methods have limited their use such as respiratory depression with intravenous opioids. Caudal block is a simple and effective technique in pediatrics with a high success rate [2].

Caudal anesthesia is the safest and easiest approach to the epidural space. Caudal block can be used as the sole anesthetic for some procedures, or as an adjuvant with general anesthesia [3]. Caudal block is a superior technique compared with spinal anesthesia because of a higher success rate, duration of recovery, and less postoperative need for analgesics [4].

Bupivacaine is the most common local anesthetic used in pediatrics by the caudal route despite the low toxic threshold in comparison with levobupivacaine. Bupivacaine is available as a racemic mixture with equal percentages of two enantiomers: dexbupivacaine (R isomer) and levobupivacaine (S isomer) [5]. Studies in animals have proven that dexbupivacaine is the cause of the excess toxicity of bupivacaine [6].

Levobupivacaine is superior to racemic bupivacaine as it provides a wider margin of safety and less postoperative motor block with the same analgesic efficacy [7]. Levobupivacaine has less affinity and strength of depressant effects on myocardium and central nervous vital centers [8].

Aim and objective

The aim of this study is to compare the efficacy of caudally administered isobaric levobupivacaine 0.25% versus isobaric bupivacaine 0.25% in children undergoing lower abdominal surgery.

Our primary outcome was the duration of sensory blockade, whereas our secondary outcomes were the onset time of sensory block and the duration of motor block.

Patients and methods

After obtaining approval from the research ethics committee (approval code: 3037/01/15) and after informed written consent was obtained from patients’ guardians, a prospective randomized single-blind study was carried out in Tanta University Hospitals in the Pediatric Surgery Department on 60 children of both sexes, 1–10 years old, American Society of Anesthesiologists I and II, scheduled for elective lower abdominal surgery. Patients whose guardians did not provide consent, patients with a history of allergy to local anesthetics, local infection or anatomic malformation at the site of the block, coagulopathies, history of seizures or known systemic diseases (renal, hepatic, respiratory, cardiac), and neurological deficits in the lower limb were excluded from the study.

Patients were randomized into two equal groups using a sealed opaque envelop (30 patients in each group) according to the local anesthetic used: group I: bupivacaine group: patients received 1 ml/kg bupivacaine 0.25% within ∼2 min and group II: levobupivacaine group: patients received 1 ml/kg levobupivacaine 0.25% within ∼2 min ([Figure 1]). The measurements were taken by another anesthetist who had no subsequent involvement in the study.

Preoperative assessment was performed by assessment of history, clinical examination, and laboratory investigations including complete blood count, bleeding time, and clotting time. Patients fasted according to American Society of Anesthesiologists guidelines. Oral midazolam 0.5 mg/kg was administered 30 min before induction. On arrival to operation room, the patients were attached to the monitor displaying the following: ECG, pulse oximetry, noninvasive blood pressure, and end-tidal CO2. Anesthesia was induced by 8% sevoflurane and 100% O2 through a face mask. When anesthesia reached an adequate depth, a peripheral venous line was inserted and a classic disposable laryngeal mask airway (size according to weight) was placed without using a neuromuscular blocker preserving spontaneous breathing. An infusion with glucose 5% in half-normal saline was administered at a rate of 5 ml/kg/h. Anesthesia was maintained by 2% sevoflurane and O2. After induction of anesthesia and securing the airway, patients were placed in the left lateral position, the region was sterilized in a craniocaudal direction with poviodine iodine 10%, sterile drapes were applied, and sterile gloves were used. The sacral hiatus was palpated and then a 23 G short needle was used with the bevel down. First, the needle was inserted perpendicular to the skin until the ligament was encountered (noted as an increase in the resistance), and then the needle was lowered to an angle of 45° to the surface of the skin and advanced through the ligament. When the loss of resistance was perceived (penetration of the sacrococcygeal ligament that occludes the sacral hiatus), the needle was lowered parallel to the skin. As the needle passes into the epidural space, the needle should only be minimally advanced, no more than 1–3 mm, to avoid a bloody puncture or an intrathecal injection. Negative aspiration was performed to exclude blood and cerebrospinal fluid. A local anesthetic was administered. A finger should be used to palpate the skin cephalad to the needle to ensure that the local anesthetic was not injected subcutaneously. Incremental doses of the medication every 20–30 s over 2 min were administered while monitoring vital signs for evidence of intravenous or intrathecal administration. Any resistance to injection was interpreted as incorrect positioning of the needle. The onset time of analgesia was assessed by applying mechanical stimuli to the skin using an Allis clamp (which provides pain stimulus to a wider area than a pinprick stimulus) ∼10 min after the caudal administration [9]. The absence of gross movements (extension or flexion of the arms and legs, chest extension, flexion of the head, abdominal contraction) and absence of a significant difference (±15%) in mean arterial pressure (MAP) and heart rate (HR) showed that analgesia was adequate and the surgery could be started.

If the analgesia was inadequate, the same mechanical stimulus was administered and the condition of analgesia was re-assessed after 5 min. In the event of the same responses (inadequacy), the block was considered to be unsuccessful, and the analgesia was considered inadequate, fentanyl 1 mg/kg was administered intravenously and the number of patients was recorded and excluded from the study. At the end of the surgery, sevoflurane was discontinued, the laryngeal mask airway removed, and the patient was transferred to the postanesthesia care unit.

Measurements

Demographic data (age, weight, and sex), type of surgery, onset time of sensory block, duration of surgery, and duration of anesthesia were determined. HR, MAP, and respiratory rate (RR) were recorded at baseline before induction of anesthesia and 5, 10, 15, 20, 25, and 30 min after anesthesia and at the end of surgery. Postoperative pain was assessed using the Children’s and Infant’s Postoperative Pain Scale (CHIPPS) ([Table 1]) and recorded postoperatively at 15, 30, 60, 120, 180, and 240 min (until the CHIPPS score was above 10). If the CHIPPS score was 10 or below, there was no need for additional analgesia. If the score was above 10, 15 mg/kg rectal paracetamol was administered. Time of postoperative first rescue of analgesia. Duration of motor blockade was assessed using the Bromage score ([Table 2]), and recorded postoperatively at 15, 30, 60, 120, 180, and 240 min (until Bromage score was 0). Any side effects during the first 24 h were recorded (nausea, vomiting, urine retention − manifestations of local anesthetic toxicity: bradycardia, convulsions, respiratory depression).

The sample size calculation was performed using the EpI-Info 2002 (CDC, Atlanta, Georgia, USA) software statistical package designed by the WHO and by the Centers for Disease Control and Prevention. The sample size was calculated to be N more than 27 on the basis of the following considerations: 95% confidence limit, 90% power of the study, and the primary outcome: duration of sensory block (on the basis of the results of a previous study [7]) to detect a significant difference of 45 min.

Statistical analysis

Statistical presentation and analysis were carried out using SPSS (IBM, USA), v.24. Results were expressed as means±SD. Student’s paired t-test was used for statistical analysis within the same group. Unpaired t-test was used for comparison of parametric data (age, weight, duration of surgery, duration of anesthesia, HR, MAP, and RR) between the two groups studied. A modified χ2-test was used for small numbers: for comparison of qualitative data (sex) between two groups. The Mann–Whitney test was used for comparison of nonparametric data (CHIPSS, Bromage score). A P-value less than 0.05 was considered significant.

Results

There was no statistically significant difference between both groups in demographic data (age, sex, and weight), type of surgery, duration of surgery, duration of anesthesia, and onset time of sensory block ([Table 1]).

There was no statistically significant difference between both groups in HR in at all time-points of measurement. HR values showed a statistically significant decrease 20 and 25 min after the administration of anesthesia compared with baseline in group I. HR values showed a statistically significant decrease 20, 25, and 30 min after the administration of anesthesia compared with the baseline in group II ([Table 3] and [Figure 2]).

There was no statistically significant difference between both groups in MAP at all time-points of measurement. MAP values showed a statistically significant decrease 15, 20, 25, and 30 min after the administration of anesthesia compared with the baseline in group I. MAP values showed a statistically significant decrease 15, 20, 25, and 30 min after the administration of anesthesia compared with the baseline in group II ([Table 4] and [Figure 3]).

There was no statistically significant difference between both groups in RR and within the same group at all time-points of measurement.

CHIPPS was significantly lower in group I than group II at 120 and 180 min postoperatively and there was no statistically significant difference between both groups at (15, 30, and 60 min) postoperatively ([Figure 4]).

The Bromage score was significantly lower in group II than group I at 15, 30, and 60 min postoperatively and there was no statistically significant difference between both groups at 120 and 180 min postoperatively ([Figure 5]).

The concept of adequate analgesia is well established in adults, but as children cannot express their feelings of pain, they were frequently ignored and given secondary importance [12].

In terms of the onset time of sensory block, there was no statistically significant difference between bupivacaine and levobupivacaine. In agreement with our study, Locatelli and colleagues found no significant difference between caudal bupivacaine 0.25%, ropivacaine 0.25%, or levobupivacaine 0.25%. Also, Frawley et al. [13] reported that there was no significant difference between 0.25% bupivacaine and 0.25% levobupivacaine (received caudally with a total volume of 1 ml/kg). Moreover, Ingelmo et al. [14] reported that there was no significant difference between bupivacaine and levobupivacaine in the analgesic onset time of the caudal block. In their study, patients were randomized to receive a caudal block with 1 ml/kg of 0.2% bupivacaine, 0.2% ropivacaine, or 0.2% levobupivacaine. Also, Kaya et al. [15] reported that there were no significant differences between bupivacaine 0.25% and levobupivacaine 0.25% in the analgesic onset time (0.5 ml/kg was administered caudally). In contrast to our study, Breschan et al. [16] concluded that the onset of analgesia was significantly later in the levobupivacaine group than the bupivacaine group (1 ml/kg 0.2%), and they did not provide any explanation.

In terms of the CHIPPS, we found that it was significantly lower in group I compared with group II at 120 and 180 min postoperatively, and there was no significant difference 15, 30, and 60 min postoperatively. In agreement with our study, Kaya et al. [15] reported that bupivacaine yielded significantly lower mean CHIPPS scores at the 15th, 30th, and 90th min postoperatively than levobupivacaine. In contrast, Breschan et al. [16] concluded that there was no statistically significant difference in CHIPPS between bupivacaine and levobupivacaine and this could be explained by the low concentration (0.2%) used in their study. Also, Sen et al. [17] observed that caudal 0.5 ml/kg of 0.125% bupivacaine and levobupivacaine were equally effective for postoperative analgesia after subumbilical surgeries in pediatric patients and this may be because of the low volume and the low concentration used in their study. Also, Sezen et al. [18] reported that no statistically significant difference in CHIPPS between both groups could be detected at any time-point of measurement and this may be explained by the use of an adjuvant (tramadol) added to a local anesthetic (in their study, patients received bupivacaine 0.25% plus tramadol 2 mg/kg (1 ml/kg) or levobupivacaine 0.25% plus tramadol 2 mg/kg (1 ml/kg) by the caudal route).

In terms of the Bromage score, we found that it was significantly lower in group II compared with group I at 15, 30, and 60 min postoperatively. In agreement with our study, Locatelli et al. [19] reported that bupivacaine produced a higher incidence of residual motor blockade than levobupivacaine. However, in patients receiving 1 ml/kg local anesthetics, there were no significant differences between the groups in residual motor block 3 h after caudal block, showing the effect of the volume on the degree of motor block. Also, Breschan et al. [16] concluded that the degree of motor block was significantly less after levobupivacaine during the first 2 h. postoperatively. In contrast to our study, Kaya et al. [15] concluded that there was no significant difference in the Bromage scores between levobupivacaine and bupivacaine. They reported that motor block cannot be compared when low doses of a local anesthetic are used; however, when a high dose of local anesthetic is used, the comparison can be made and the residual motor block goes in parallel with the increasing drug concentration (>0.175%). They did not observe any difference in motor block, which might be because of the low doses of local anesthetics used. However, Sen et al. [17] showed no significant differences between levobupivacaine and bupivacaine, and this may be attributed to the low volume and the low concentration used in their study. Moreover, Sezen et al. [18] concluded that they found no residual block at the postoperative second hour in either group (bupivacaine plus tramadol and levobupivacaine plus tramadol) and this may be explained by the use of an adjuvant (tramadol) added to the local anesthetic.

In terms of the time of postoperative first-rescue analgesia, we found that it was significantly earlier in group II compared with group I. In agreement with our study, Locatelli et al. [19] found that bupivacaine produced a longer analgesic block compared with levobupivacaine. In contrast to our study, Breschan et al. [16] concluded that there were no significant differences between levobupivacaine and bupivacaine in the time of postoperative first-rescue analgesia, and this may be attributed to the low concentration in their study. However, Sen et al. [17] observed that there were no significant differences between levobupivacaine and bupivacaine in the time of postoperative first-rescue analgesia and this may be explained by the low volume and the low concentration used in their study. Moreover, Sezen et al. [18] showed that there were no significant differences between levobupivacaine and bupivacaine in the time of postoperative first-rescue analgesia and this may be because an adjuvant (tramadol) was added to the local anesthetic.

Conclusion

Using similar doses, bupivacaine led to a higher incidence of residual motor block and longer analgesic block than levobupivacaine. Thus, levobupivacaine is more suitable for short operations and could make it preferable for day case surgery. However, bupivacaine is still more suitable for prolonged operations.

Acknowledgements

All authors played an equal role in design, work, statistical analysis, and manuscript writing.